EFFECTS OF ANIONS ON THERMALLY-INDUCED WHEY-PROTEIN ISOLATE GELS

Fundamental fracture, water-holding and microstructural properties of thermally induced whey protein isolate gels containing one of two divalent, stabilizing anions (sulfate and phosphate) or one monovalent, chaotropic anion (thiocyanate) were investigated. All of the salts produced similar overall trends in stress and strain; however, transition points were salt specific. At ionic strengths 0.09 less than or equal to mu less than or equal to 0.50, Na2SO4 and NaSCN produced strain values of very similar magnitudes. At low salt concentrations, gel matrices were fine-stranded and hem water well. As salt concentrations increased gel matrices became particulate and water-holding capacities decreased. Promotion of the particulate matrix formation folio wed the Hofmeister series (SO42- > HPO42- >>> SCN-). The calcium chelating ability of phosphate was responsible for inhibiting particulate matrix formation. Optical density trends, reflecting stabilizing or chaotropic properties of each anion, indicated that differences between sulfate- and phosphate-containing gels could not be explained by Hofmeister-type stabilizing propensity.